Role of reactive oxygen species (ROS) in MAPK-mediated chemotropism and infectious growth of the plant pathogenic fungus Fusarium oxysporum

趋化性，即朝着化学梯度方向生长，控制着真菌的基本过程，如养分获取、性或无性融合和宿主感染。趋化分子的性质，以及趋化受体和下游信号通路在很大程度上是未知的。Córdoba大学的宿主小组开发了一种定量测量真菌植物病原体尖孢镰刀菌的定向菌丝生长的方法。通过对趋化机制的遗传剖析，鉴定出丝裂原活化蛋白激酶（MAPK） Mpk1是尖孢镰刀菌对寄主植物信号的趋化反应的重要组成部分。此外，根分泌物中的主要化学引诱剂被鉴定为植物分泌的过氧化物酶，这表明活性氧（ROS）在mapk介导的趋化信号传导中起作用。在此，我们提出：1)研究生成ros的酶NADPH氧化酶（Nox）在调控MAPK信号和趋化生长中的作用，通过测定氧化孢子菌Nox缺失突变体的MAPK磷酸化状态和趋化反应；2)利用半胱氨酸捕获亚磺酸状态和位点定向诱变，鉴定被ros依赖性过氧化物酶活性修饰的真菌靶蛋白。我们预计这些结果将揭示ROS和MAPK信号在指导真菌致病性的基本过程中的新分子联系和下游靶点。这一知识将有助于开发新的抗真菌药物。总体而言，本项目结合了申请人和主办单位在真菌ROS信号和趋化生长方面的经验。此外，它允许申请人在国际公认的研究小组中从事前沿研究课题，为她未来几年在德国进行创新研究提供最佳准备。

Chemotropism, the directed growth towards a chemical gradient, governs essential processes in fungi such as nutrient acquisition, sexual or asexual fusion and host infection. The nature of the chemoattractant molecules, as well as the chemotropic receptors and downstream signaling pathways are largely unknown. The host group at University of Córdoba has developed a method to quantitatively measure directed hyphal growth in the fungal plant pathogen Fusarium oxysporum. Genetic dissection of the chemotropic mechanism led to the identification of a mitogen-activated protein kinase (MAPK), Mpk1, as an essential component in the chemotropic response of F. oxysporum to host plant signals. Moreover, the major chemoattractant in root exudates was identified as a plant-secreted peroxidase, suggesting a role of reactive oxygen species (ROS) in MAPK-mediated chemotropic signaling. Here we propose to 1) study the role of the ROS-generating enzymes NADPH oxidases (Nox) in regulation of MAPK signaling and chemotropic growth, by determining MAPK phosphorylation status and chemotropic response in F. oxysporum nox deletion mutants and 2) to identify fungal target proteins that are modified by the ROS-dependent activity of the peroxidase, using cysteine trapping in sulfenic acid state and site-directed mutagenesis. We anticipate that the results will uncover novel molecular links and downstream targets of ROS and MAPK signaling in fundamental processes guiding fungal pathogenicity. This knowledge will be of interest for the development of new anti-fungal drugs. Overall, this project combines the experiences of the applicant and the host institute regarding ROS signaling in fungi and chemotropic growth, respectively. Further, it allows the applicant to work on a cutting-edge research topic in an internationally recognized research group providing her with optimal preparation to undertake innovative research in Germany in the upcoming years.